Carbon Fiber hiking poles, with a strap.
These are very light weight, he can choose the base to match the conditions, and they are not expensive.
I use a pair to hunt and hike with, plus you can use them as shooting sticks.
I got my dad a pair. They are very hard to beat.
https://www.amazon.com/dp/B00EJP43FA?ref=emc_b_5_iThey sell a similar pair at costco.